1,720,968 research outputs found
Electrochemical conversion of carbon dioxide in pressurized electrochemical cells
No full textTo limit the negative effect of carbon dioxide as a greenhouse gas, an interesting approach is the utilization of Carbon Capture and Conversion (CCC) methodology, which is focused on the use of CO2 waste as a feedstock to produce added-value products by using the excess electric energy from renewable source [1]. In this framework, an increasing attention has been devoted to the electrochemical conversion of carbon dioxide to formic acid in water [2-3] or CO [1]. Since the main hurdle of the CO2 reduction from aqueous solution is the low CO2 solubility in water, in this work, the utilization of pressurized electrochemical cells is evaluated. The effect of various operating parameters, including pressure, current density, and flow rate, on the conversion of CO2 at tin flat cathodes is also presented and discussed.
[1] G. Wu and P. Zelenay, Accounts Chem. Res., 2013, 46, 1878–1889.
[2] L. Monico, K. Janssens, E. Hendriks, F. Vanmeert, G. Van der Snickt, M. Cotte, G. Falkenberg, B. G. Brunetti, and C. Milani, Angew. Chem. Int. Ed. 2015, 54, 13293-13297.
[1] S. Ma, P. J. Kenis, Current Opinion in Chemical Engineering, 2013, 2, 191-199.
[2] A. Del Castillo, M. Alvarez-Guerra, J. Solla-Gullòn, A. Sàez, V. Montiel, A. Irabien, J. CO2 Util.. 2017, 18, 222–228.
[4] O. Scialdone, A. Galia, G., Lo Nero, F. Proietto, S. Sabatino, B. Schiavo, Electrochimica Acta, 2016, 199, 332-341
Electrochemical conversion of carbon dioxide to formic acid at Sn and BDD cathodes
No full textElectrochemical reduction of CO2 to useful compounds in the aqueous electrolyte has been actively investigated as alternative technologies to contribute to curbing the rising levels of CO2 in the atmosphere. Many researchers have focused on the CO2 reduction to formic acid, which is considered one of the main target-products owing to its usefulness for agriculture, chemical and pharmaceutical industry, and it is expected to be a good hydrogen storage medium for an upcoming H2-energy-based society [1,2].
In the last few years, an increasing attention was devoted to the utilization of tin electrode for its low cost, low toxicity as well as the high selectivity towards the synthesis of formic acid [2]. Recently, it was shown that boron-doped diamond (BDD) used as working electrode could be a promising material for the production of formic acid by CO2 reduction characterized by high stability and high faradic efficiency at low current density. In this work, the electrochemical conversion of CO2 in water solution using both tin and BDD cathode was systematically investigated to compare the performances achieved at these two electrodes.
[1] M. Tomisaki, K. Natsui, N. Ikemiya, K. Nakata, and Y. Einaga, ChemistrySelect, 2018, 3.36, 10209-10213.
[2] O. Scialdone, A. Galia, G. Lo Nero, F. Proietto, S. Sabatino, and B. Schiavo, Electrochimica Acta, 2016, 199, 332-341
How far are we from the valorization of waste-CO2 to formic acid via electrochemical routes for the applicative scale?
No full textTo date, the decarbonization of the world economy and storage and production of energy from alternative C-based sources is considered a relevant topic. The electrochemical conversion of CO2 has been widely investigated since the 1870s as a promising strategy to convert waste-CO2 into value-added chemicals [1,2].
Recently, it was highlighted that, among the several emerging technologies for CO2 conversion to value-added products on an applicative scale, electrochemical technologies are the closest to commercialization due to the numerous start-ups and established companies being invested in this area (e.g., Opus-12, Dioxide Material, and Carbon Recycling International) [3]. These technologies have attracted attention due to some unique advantages (including operating at low temperature, easy scale-up stages, use of excess electric energy from intermittent renewable sources, and small environmental impact). However, to be suitable at an industrial scale, the process should present simultaneously high current densities, faradaic efficiencies close to 100%, high concentrations and long-term stability [4].
The objective of this work is to show how far this technology is from being implemented on an industrial scale and to critically discuss the main strategies to improve the process for the synthesis of formic acid/formate. To conclude, a technical-economic overview will be discussed, highlighting the main factors that affect the scalability of the process on an industrial scale.
[1] A.S. Reis Machado et al. Curr. Opin. Green Sustain. Chem. 2018, 11, 86 [2] W. Zhang et al. Adv. Sci. 2018, 5, 1700275.
[3] O.S. Bushuyev et al. Joule 2018, 2, 825.
[4] F. Proietto et al. Electrochim. Acta 2021, 380, 138753
Effect of the air pressure on electro-Fenton process
Full text linkElectro-Fenton process is considered a very promising tool for the treatment of waste waters contaminated by organic pollutants refractant or toxic for microorganisms used in biological processes [1-6]. In these processes H2O2 is continuously supplied to an acidic aqueous solution contained in an electrolytic cell from the two-electron reduction of oxygen gas, directly injected as pure gas or bubbled air. Due to the poor solubility of O2 in aqueous solutions, two dimensional cheap graphite or carbon felt electrodes give quite slow generation of H2O2, thus resulting in a slow abatement of organics.
In this context, we report here a series of studies [7-9] on the effect of air pressure on the electro-generation of H2O2 and the abatement of organic pollutants in water by electro-Fenton process. The effect of air pressure, current density, mixing and nature of the organic pollutant was evaluated.
[1] E. Brillas, I. Sirés, M.A. Oturan, Chem. Rev., 109 (2009) 6570-6631.
[2] C.A. Martínez-Huitle, M.A. Rodrigo, I. Sirés, O. Scialdone, Chem. Rev. 115 (2015) 13362–13407.
[3] M. Panizza, G. Cerisola, Chem. Rev. 109 (2009) 6541–6569.
[4] I. Sirés, E. Brillas, M.A. Oturan, M.A. Rodrigo, M. Panizza, Environ. Sci. Pollut. Res. 21 (2014) 8336–8367.
[5] C.A. Martínez-Huitle, S. Ferro, Chem. Soc. Rev. 35 (2006) 1324–1340.
[6] B.P.P. Chaplin, Environ. Sci. Process. Impacts. 16 (2014) 1182–1203.
[7] O. Scialdone, A. Galia, C. Gattuso, S. Sabatino, B. Schiavo, Electrochim. Acta, 182 (2015) 775-780.
[8] J.F. Pérez, A. Galia, M.A. Rodrigo, J. Llanos, S. Sabatino, C. Sáez, B. Schiavo, O. Scialdone, Electrochim. Acta, 248 (2017) 169-177.
[9] A.H. Ltaïef, S. Sabatino, F. Proietto, A. Galia, O. Scialdone, O. 2018, Chemosphere, 202, 111-118
Electrochemical conversion of CO2 to formic acid using a Sn based electrode: A critical review on the state-of-the-art technologies and their potential
No full textThe electrochemical conversion of carbon dioxide is considered one of the most promising strategies to convert waste-CO2 into value-added chemicals. This review focuses on the synthesis of formic acid/formate in aqueous electrolyte using Sn-based cathodes; this material is considered relatively cheap and shows promising results in terms of faradaic efficiency. In order to be suitable at an industrial scale, the process should present simultaneously high current densities, faradaic efficiencies close to 100%, high concentrations of formic acid and long-term stability. Analysing the main results reported in the literature, it was observed that to date further studies are necessary to achieve this outcome. Several strategies that can be used to overcome the main bottlenecks of the process were presented and critically reviewed. Finally, to evaluate the main factors that affect the scalability of the process on an industrial scale, a technical-economic overview was discussed
Electrochemical treatment of wastewater contaminated by organics and containing chlorides: Effect of operative parameters on the abatement of organics and the generation of chlorinated by-products
Full text linkIn the last years, large attention has been devoted to the electrochemical treatment of wastewater polluted by recalcitrant organics and containing chlorides. However, the utilization on an applicative scale of this route is limited by the fact that usually it is not possible to achieve high removals of organics without the generation of significant amounts of chlorinated by-products. Here, the role of several operative parameters on the performances of the process was systematically evaluated using phenol as a model organic pollutant. It was shown that the removal of phenol and TOC and the generation of many by-products including chlorophenols, chloroacetic acids, chlorate and perchlorate dramatically depend on the adopted operative conditions (i.e., nature of anode and cathode, current density and concentration of chlorides). The use of boron doped diamond (BDD) anode gave the highest removal of TOC but also the highest final concentrations of chlorate and perchlorate and the lowest concentrations of chloroacetic acids. Conversely, the use of Ti/IrO2-Ta2O5 gave the lowest generation of chlorate and no perchlorate. The use of lower current densities allowed as well to reduce the concentrations of these compounds. It is worth to mention that lower amounts of chlorinated by-products were achieved using suitable cathodes. Carbon felt cathodes, as previously reported for the water disinfection, allowed to reduce the generation of chlorate. Moreover, it was shown, for the first time, that the use of silver cathodes minimized the concentrations of chloroacetic acids. In addition, it was found that the use of a system equipped with both silver and carbon felt cathodes and proper current densities allowed to increase remarkably the removals of TOC and the current efficiency and to achieve very low concentrations of chlorinated by-products
Phenol abatement in a microfluidic reactor
No full textIn this work a commercial undivided filter press flow cell equipped with one or more polytetrafluoroethylene spacers of micrometric thikness was used in order to evaluate the performances of this device for the degradation of phenol by anodic oxidation in the presence of chlorides
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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